1. Field of the Disclosure
A method of forming a barrier metal in a semiconductor device is disclosed that is capable of preventing introduction of a conductive material into a base layer by a subsequent process, by forming the barrier metal after pores existing on the surface of an interlayer insulating film being a porous film are buried.
2. Background of the Related Art
As the degree of integration in the semiconductor device is increased, the distance between the metal lines is narrowed. Accordingly, there is a problem that the speed of the device is reduced since the parasitic capacitance between the metal lines is increased. In order to solve this problem, it is required that copper (Cu), etc. having a low resistivity and a good electrical conductivity be used as a material of the metal line instead of aluminum or tungsten that has been currently used. A low dielectric constant film is needed to be used as the insulating film instead of the existing oxide film having a dielectric constant of 4.
The low dielectric constant film includes an organic polymer film, an inorganic SiOC film and a porous film having porosities therein. Of them, the organic polymer film and the inorganic SiOC film have a dielectric constant of about 2.7, which is relatively high among the low dielectric constant film.
The porous film can improve a low dielectric constant characteristic by controlling the ratio of the pore within the film. This porous material is made by a method by which air bubbles of a small size are formed within the film in the course of curing a precursor of a solid state or a weak coupling between TEOS particles being the precursor, and a solvent is abruptly volatilized to keep the porous structure intact. In this process, silica mesh count within the porous material and the pore structure are changed depending on a drying method of the solvent. If the solvent is volatilized by an annealing process like the curing of the SOG film, a material having a dense structure is formed while the porous material shrunk, so that it does not have a desired characteristic of the porous film having a low dielectric constant. Therefore, the porous material is formed by means of a supercritical drying method of abruptly volatilizing the solvent in a condition of over a triple point in the solvent. Another method includes making precocious the solvent as a special solvent at the normal pressure to form the porous material. As the pore has a dielectric constant of 1 in the air, it is required that the ratio of the pore be increased or the dielectric characteristic of silica be lowered in order to form a film of a low dielectric constant. In case of the former, however, if the ratio of the pore is increased, mechanical stability is lowered since a structural strength of the film is weaken. For this reason, there is a problem that the low dielectric constant film could not hold the weight when a subsequent CMP process, etc. implemented.
A method of manufacturing the semiconductor device using the above porous film will be described by reference to FIG. 1A and FIG. 1B.
Referring to FIG. 1A, a first SiC layer 12, a porous film 13 and a second SiC layer 14 are formed on a base layer 11. A via hole 10 trough which a part of the base layer 11 is exposed is then formed by a patterning process. As described above, a plurality of pores 15 are formed in the porous film 13. In particular, pores 16 are formed at the sidewalls of the via hole 10.
By reference to FIG. 1B, a barrier metal 17 is formed on the entire structure including the via hole 10. At this time, the barrier metal 17 is broken off due to the pores at the sidewalls of the via hole 10, so that a broken-off region 18 is formed. In the porous film, the size of the pore is approximately 10˜40 Å and the density of the pore is about 30˜50%. Copper is infiltrated into the base layer 11 due to discontinuity of this barrier metal when a subsequent seed metal, copper, etc. buried, which degrades the characteristic of the device.